But a crafty line-out move caught the Irish flat-footed as Mike Phillips broke away to score, though Wales had used a different ball at the line-out.

James Hook converted that score and kicked three out of four penalties as Wales survived a late Irish onslaught.

The visitors, needing a converted try to sneak victory, had created an overlap in the left corner.

But replacement Paddy Wallace, with Keith Earls outside him, opted to cut back inside, perhaps conscious of trying to make the conversion easier, and the chance was eventually lost.

Ireland had lost only once in Cardiff since 1983, winning 10 games and drawing one in their past 12 visits, including their last visit in 2009 when a 17-15 win secured their first Grand Slam for 61 years.

But Wales upset that pattern to maintain their momentum after back-to-back victories in Scotland and Italy.

Warren Gatland's men now travel to France, shocked by their first ever defeat in Italy earlier on Saturday, with a sniff of the championship if either Scotland or Ireland can derail England's title charge.

Wales, having been led out by 50-cap men Phillips and Ryan Jones, made a nervy start from Ireland's kick-off as Lee Byrne's attempted clearance was charged down by Eoin Reddan.

Unfortunately for the scrum-half he took the full force of the ball in his face and that was the end of his game after just one minute, with Peter Stringer coming on to replace the stricken Leinster man.

Stringer had an immediate impact as he drew several Welsh defenders before off-loading to Tommy Bowe, who in turn sent O'Driscoll over the line for the opening try.

O'Driscoll try equals Nations record

With that score the celebrated centre equalled Scotland great Ian Smith's championship try record of 24 from 78 years ago, while Ronan O'Gara's conversion saw the fly-half become the fifth man to reach 1000 Test points.

O'Gara nearly conjured a second breakthrough with a chip over the top that Luke Fitzgerald did well to gather.

But Wales lock Alun Wyn Jones dug deep at the breakdown to turn over possession and set up a counter.

The home side suffered their own early injury blow on 13 minutes when prop Craig Mitchell was forced off with a dislocated shoulder, to be replaced by John Yapp.

Yapp went to loose-head, with Paul James shifting across the front row to take up the tight-head role.

Despite that setback Wales worked their way into the Irish 22 thanks to a perceptive long punt by Byrne.

Ireland coughed up a penalty under pressure in defence but Hook saw his kick from tight on the left touchline ricochet back off the post.

Ireland gathered but O'Gara was unable to get much distance on his touch-finder and Wales launched another series of forays from the line-out.

Ireland's discipline again failed them, but this time in front of the posts, Hook sent his kick sailing through the uprights for Wales' first points.

One Ireland player firmly on his defensive game was Tommy Bowe, the wing seemingly having some inside knowledge of Welsh intentions thanks to his Ospreys training.

Bowe's regional team-mate Shane Williams was catching the eye for Wales with some typical broken play runs, while flanker Sam Warburton was always on the attacker's shoulder in support.

Another penalty for not rolling away at a ruck allowed Hook to kick his second penalty, bringing Wales back to just 6-7 behind as the half-hour mark approached.

But Ireland soon restored their four-point lead when James was penalised for collapsing a scrum and O'Gara dissected the posts from the 10-metre line.

Wales replied with a long-range Leigh Halfpenny kick just inside the Irish half, only for the visitors to surge towards the Welsh posts thanks to Sean O'Brien's bullocking run.

Ireland swung left, spotting space outside, but the crucial pass went between Fitzgerald's legs with the line at his mercy.

But Ireland had the consolation of a penalty conceded by the scrambling Wales defence and O'Gara kicked his side to a 13-9 lead at the break.

A steady drizzle descended through the open Millennium Stadium roof as the second half got under way, making what were already slippy conditions more treacherous.

Equally slick was the way Wales took the lead, as Matthew Rees picked out Phillips peeling around the front of a line-out.

The move caught Ireland napping and the scrum-half streaked away down the left touchline to score in the corner, Hook converting for a 16-13 lead.

Ball mix-up gifts Wales controversial try

But TV replays showed that in taking a quick throw-in, Rees had used a different ball - handed to him by a ball-boy - to the one that Jonny Sexton had sliced into touch, which is against rugby's Law 19.2.

When referee Jonathan Kaplan asked his Scottish touch judge Peter Allan 'Is it the correct ball?' however, Allan answered in the affirmative and Kaplan awarded the try, much to the evident anger of the Irish side.

The visitors almost hit back immediately, only for Donncha O'Callaghan to pass forward to Fitzgerald as the full-back burst over the line.

Referee Jonathan Kaplan had been playing advantage, though, giving Jonathan Sexton - on for O'Gara - the chance to level the scores but the fly-half sent his kick wide.

As the game entered its final quarter Ireland battered away at the Welsh 22, with Paul O'Connell leading his troops by example.

But the red shirts defended with bravery and discipline to hold out, eventually turning over possession to lift the siege.

Hook added his fourth penalty to give Wales some breathing space on the scoreboard and open a six-point gap.

A frantic final five minutes saw Wales hanging on by their finger-tips, as Ireland stretched them one way then the other.

A gaping overlap opened up on the left but Paddy Wallace opted to cut back inside rather than present Earls with a certain try, and Ireland's last hope was gone.

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